Field of the Invention
This invention is directed toward useful tools in the garage door repair and installation industry. In particular, the embodied tool is used to take a measurement that is helpful in the design, installation, and repair of garage door counterbalance springs.
Description of Related Art
Sectional garage doors are known in the art. Although the design of sectional garage doors can vary, certain components are common to garage door systems. A typical sectional garage door has a number of panel sections—usually four—that are hinged together at their upper and lower horizontal edges. A number of hinges with horizontal pins are incorporated into the door sections to allow the door to be lifted vertically and then rotate 90 degrees through a track system. The door sections include a number of rollers that ride in a track on either side of the garage door.
Some garage doors are large and heavy by being made from a thick wood, and some are very light by using aluminum or light gauge steel panels. Since a garage door is relatively large, it is normal to provide a spring counter balance system so as to make opening relatively easy no matter the weight. The springs are usually one of two styles: extension or torsion.
Extension springs are often used with a simple cable system to facilitate economy and a relatively smooth force over the entire lift. As the door is lifted, the amount of force needed to lift the door reduces, and the extension spring is well adapted to this situation.
Similarly, torsion springs also counterbalance the door. They are typically a wound wire surrounding a torsion bar that is connected to the garage door by a drum/cable. The springs have a designed cycle life, based on the number of operations. Periodically, the springs break and need to be replaced.
The torsion counterbalancing springs are designed using an inch pounds per tum (IPPT) criterion using parameters such as the weight of the door, the number of cycles, the size of the drum that is used on the torsion bar, and other factors.
The torsion spring is connected to a torsion bar, which in tum is connected to a cable drum on either side of the door. A lifting cable from the drum is connected to the lower edge of the door. When the door is lowered, the withdrawal of the cable from the drum causes the shaft to turn, which winds up the torsion spring. Typically, one or two torsion springs are chosen so that the counterbalancing force provides an acceptable and smooth lifting force, and an acceptable life.
As stated previously, spring failure is a common occurrence, and the selection of a replacement spring is fraught with difficulties. A spring is properly designed using a number of variables to provide acceptable life and a smooth operation. Repairmen who face broken springs often will select a spring that is a direct replacement for the failed spring. However, if the door failure is related to an improperly designed spring(s), the problem will re-occur. The repairman often assumes the original design was correct. It is much preferred to check the spring design when repairing a broken door.
Proper spring design is inconvenient for a repair man, and the repair man must currently take a number of steps to determine the required spring. The length of time to make a new selection and the ability to get all the information needed for the design hinders the effort. In particular, the door weight is awkward to obtain and the use of a bathroom scale is often the method used.
What is needed is a method to provide the repairman the calculation tool needed, and a simplified procedure to obtain the door weight.